Antibody drug conjugate (ADC) are antibodies that are conjugated, via chemical linkers, to cytotoxic agents. ADCs leverage an antibody's binding specificity for its target to deliver cytotoxic agents to an abnormal cell. Traditional ADC technology involves chemically attaching a drug, through a linker, to particular amino acid residues of the antibody. For example, the linker can be attached to the antibody at the sulfhydryl groups of one or more cysteine residues within the antibody heavy and/or light chains. A recognized problem with conjugation at cysteine residues, however, is that the process requires disrupting one or more interchain disulfide bonds which ordinarily serve to maintain the structure and function of the antibody molecule. Cysteine-conjugated ADCs can have reduced stability, which potentially impedes the binding and therapeutic properties of the ADC. Thus, there is a need for techniques for conjugating an antibody at its cysteine residues that do not significantly impact the antibody's binding affinity, e.g., methods of conjugation that reconnect cysteine residues of an interchain disulfide bond cleaved during the conjugation process.